The goal of this project is to study 1) the mechanism by which RNA primers work in initiation of DNA synthesis in RNA tumor viruses (RSV and MLV), and 2) to study the host cell DNA for genes which synthesize primer RNA and for the provirus DNA. The mechanism of primer function will be pursued by a continuation of our work on requirements for binding of primer RNA to purified reverse transcriptase and to S35 template RNA. We shall specifically hydrolyze the primer into 5' or 3' half or quarter molecules and test the isolated fragments for activity. We shall also investigate the effect of modification of the 3' end (to which nascent DNA is attached) or the G-psi-psi-C-pu sequence (which is an unusal feature of the two primers that have been isolated, to date). Interaction with the S35 RNA will also include localization of the precise place on the template to which primer binds, and an analysis of the nucleotide sequence of that region. The studies on cell DNA will be performed using RNA-DNA hybridization in agarose gels to restriction endonuclease fragments of DNA isolated from infected or uninfected cells. We intend to study possible changes in the pattern of DNA fragments capable of hybridizing to primer or template RNAs as a function of infection. These results will help us to understand the mechanism of provirus DNA integration and perhaps cell DNA reorganization.